We report the results of a study designed to assess and evaluate how the law shapes the public health system's preparedness activities. Based on 144 qualitative interviews conducted in nine states, we used a model that compared the objective legal environment with how practitioners perceived the laws. Most local public health and emergency management professionals relied on what they perceived the legal environment to be rather than on an adequate understanding of the objective legal requirements. Major reasons for the gap include the lack of legal training for local practitioners and the difficulty of obtaining clarification and consistent legal advice regarding public health preparedness. Narrowing the gap would most likely improve preparedness outcomes. We conclude that there are serious deficiencies in legal preparedness that can undermine effective responses to public health emergencies. Correcting the lack of legal knowledge, coupled with eliminating delays in resolving legal issues and questions during public health emergencies, could have measurable consequences on reducing morbidity and mortality.